A Howler is not used for just any message, as true to their name, they are extremely loud – according to the text, a hundred times as loud as one's natural voice, though that could be simply the apparent effect. Additionally, if not opened promptly, they tend to explode: though we do not see that happening, Neville advises Ron that it is better to open one immediately and take the amplified scolding, rather than leaving it unopened and letting it explode; and Percy comments in Harry Potter and the Goblet of Fire that exploding Howlers have been scorching his desk.